Control system for a punch press

ABSTRACT

The control system is for a punch press having a reciprocatable bolster plate, and requires that run buttons of the system be depressed and held in place in order to energize first and second relays which control a bolster-in solenoid for a bolster-in actuating means. The energization of the bolster-in solenoid causes the bolster-in actuating means to move the bolster plate from a load position at the front of the press to a work position at the rear of the press. The bolster plate, as it nears the rear of the press, trips a first limit switch completing a holding circuit for the first relay and, upon arriving at the rear of the press, trips a second limit switch to deenergize the bolster-in solenoid. Both run buttons must be released simultaneously in order to energize a third relay and a ram solenoid thereby causing reciprocation of a ram. A third limit switch responsive to the cycling of the ram deenergizes the first, second and third relays at the conclusion of each cycle. Contacts of the first and third relays, operative upon deenergization, close and thus complete a circuit to the bolster-out solenoid thereby causing the bolster-out actuating means to move the bolster plate to the load position.

United States Patent [1 1 Newman Sept. 3, 1974 CONTROL SYSTEM FOR APUNCH PRESS [75] Inventor: Thomas R. Newman, Milwaukee,

Wis.

[73] Assignee: Square D Company, Park Ridge, 111.

[22] Filed: June 18, 1973 21 Appl. No.2 371,029

[52] US. Cl 72/25, 72/421, 72/444, 72/448, 83/400, 100/53, 100/DIG. 18[51] int. Cl B21j 9/20 [58] Field of Search 72/25, 448, 444, 421;100/53, DIG. 18; 83/400 [56] References Cited UNITED STATES PATENTS3,056,481 l0/1962 Luenser 100/53 3,446,106 5/1969 Ferris 83/4003,578,123 5/1971 Freeland 100/53 3,628,357 12/1971 Luenser 100/533,749,005 7/1973 Einecker 100/53 Attorney, Agent, or Firm-Harold .1.Rathbun; William V H. Schmeling [5 7] ABSTRACT The control system is fora punch press having a reciprocatable bolster plate, and requires thatrun buttons of the system be depressed and held in place in order toenergize first and second relays which control a bolster-in solenoid fora bolster-in actuating means. The energization of the bolster-insolenoid causes the bolster-in actuating means to move the bolster platefrom a load position at the front of the press to a work position at therear of the press. The bolster plate; as it nears the rear of the press,trips a first limit s witch completing a holding circuit for the firstrelay and,

' upon arriving at the rear of the press, trips a second limit switch todeenergize the bolster-in solenoid. Both run buttons must be releasedsimultaneously in order to energize a third relay and a ram solenoidthereby causing reciprocation of a ram. A third limit switch responsiveto the cycling of the ram deenergizes the first, second and third relaysat the conclusion of each cycle. Contacts of the first and third relays,operative upon deenergization, close and thus complete a circuit to thebolster-out solenoid thereby causing the bolsterout actuating means tomove the bolster plate to the load position.

4 Claims, 2 Drawing Figures CONTROL SYSTEM FOR A PUNCH PRESS BACKGROUNDOF THE INVENTION The present invention relates to a control system for ametal forming press of the type having a bolster that moves from aloading area to a work area prior to operation of a ram of the press,and more particularly to such a system including means to insure thatthe operators hands are outside the work area when the ram descends.

The concept of requiring an operator of a metal forming press tomaintain two push buttons depressed while the press is operating is notnew. Such systems increase safety because both of the operators handsmust be held on the respective push buttons during operation of thepress and the buttons are located remote from the work area. Physicalharm upon accidental or inadvertent tripping of the associated press ramis thereby avoided. Such systems, however, are easily defeated by shortcircuiting or wedging down one of the push buttons so that only one handis needed to depress the remaining push button thereby to activate thepress. A hazard arises because the operator may then place his otherhand into the press and receive physical injury as a result of the pressram coming down unexpectedly. The foregoing has been true ofconventional presses as well as those that provide for loading of apress outside of the work area.

SUMMARY OF THE INVENTION According to the present invention there isprovided an improved control system for a punch press having areciprocatable bolster plate and ram. The system comprises a pluralityof push buttons, electromagnetic relays, and limit switches whichcontrol solenoids which control movement of the movable parts of thepress.

Upon depressing two run buttons of the system, first and secondelectromagnetic relays are energized. Energization of the first relayopens contacts in a bolster-out circuit and closes contacts in abolster-in circuit. A bolster-in solenoid is thus energized therebycausing operation of a bolster-in actuating means.

As the bolster moves inwardly from a load to a work position, release ofeither one or both of the run buttons causes deenergization of thebolster-in solenoid and the energization of a bolster-out solenoidthereby to reverse the direction of movement of the bolster and thusreturn it to the load position. If both of the run buttons remaindepressed, the bolster continues its inward movement to the workposition and trips a first limit switch as it nears its work positionwhich'completes a holding circuit for the first relay.

When the bolster plate arrives at its work position, it trips a secondlimit switch which deenergizes the bolster-in solenoid thereby stoppingthe inward movement of the bolster. At this point in the cycle, acircuit to a ram solenoid which controls the tripping of the press ramautomatically becomes energized if both run buttons are releasedsimultaneously or within a limited interval of time from each other. Ifrelease of the second run button is delayed for a predetermined time,the second relay opens a contact in the ram solenoid circuit therebyprecluding operation of the ram actuating means and closes anothercontact in the bolster-out solenoid circuit causing the bolster to moveoutwardly to the load position.

If both run buttons are released simultaneously or within a shorttime-of each other, a third relay is energized before the second relayoperates. A by-pass contact of the third relay then locks in the ramsolenoid circuit thereby causing operation of the ram actuating meansbefore the second relay drops out. A third limit switch is responsive tocycling of the ram actuating means and deenergizes the first, second andthird relays after each cycle. Normally closed contacts of the first,

second and third relays then cause energization of a circuit to thebolster-out solenoid causing the bolster-out actuating means to move thebolster outwardly to the load position.

It is an object of this invention to provide an improved control systemfor a punch press which requires that both hands of an operator depressrespective run buttons in order to initiate and continue operation ofthe press.

It is a further object of this invention to provide an improved controlsystem including means to preclude the short circuiting or wedging downof one of two run buttons in an attempt to operate the press with onlyone run button.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages oftheinvention will become apparent from the following detailed descriptionwherein reference is made to the accompanying drawings, in which:

FIG. 1 is a side elevation view of a punch press of the type to whichthis invention can be applied; and

FIG. 2 is a schematic wiring diagram illustrating a preferred embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings, thecontrol system includes four limit switches 11, 12, 13 and 14, a pair ofpush buttons 21 and 22, and three electromagnetic relays 31, 32 and 33.The relays 31, 32 and 33 are represented schematically in FIG. 2 byoperating windings 31w, 32w and 33w, respectively, and the contacts 31ato 31d; 32a and 32b; and 33a to 330, respectively. The limit switchesand push buttons are shown in FIG. 1 as mounted on a punch press 34 andare shown schematically in the wiring diagram of FIG. 2.

Referring now more particularly to FIG. 2, power for the control systemis supplied from a suitable source indicated by conductors L1 and L2.The limit switch 1 1 has a normally closed contact 1 1a, and the limitswitch 12 has two normally open contacts 12a and 12b and two normallyclosed contacts and 12d. The limit switch 13 has a normally open contact13a and a normally closed contact 13b, and the limit switch 14 has anormally open contact and a normally closed contact 14b. The push button21 has a normally open contact 21a and a normally closed contact 21b,and the push button 22 has a normally open contact 22a and a normallyclosed contact 22b. The relay 31 has three normally open contacts 31a,31b and 31c and a normally closed contacts 31d; the relay 32 has anormally open contact 32a and a normally closed contact 32b; and therelay 33 has two normally open contacts 33a, and 33b and a nomiallyclosed contact 33c.

To provide for a time delay in the drop out of the relay 32, a diode 35is in series with the winding 32w and a capacitor 36 is in parallel withthe winding 32w.

The control system is designed for use with a punch press of the generaltype shown in Ferris et al. US. Pat. No. 3,446,106 issued May 27, 1969to which reference may be had for a complete description. Referring toFIG. 1, a ram 38 of the punch press 34 is reciprocated by a drivemechanism including a fly wheel 41 driven by a motor 42. The ram carriesthe upper portion of a die (not shown) which cooperates with a lower die(not shown) on a bolster plate 44. The bolster plate 44 is movedinwardly and outwardly by a hydraulic actuating means controlled by afour-way detent valve (not shown), which is operated by a pair ofsolenoids 45 and 46 having windings 45w and 46w (FIG. 2), respectively.

As described more completely in the Ferris et a1. patent, the limitswitch 12 is operated by the bolster 44 as it moves inwardly and nearsthe work position, and the limit switches 13 and 14 are operated by thebolster when it reaches its innermost or work position. A clutch (notshown) associated with the fly wheel 41 is controlled by a hydraulicvalve (not shown), which is operated by a solenoid 47 having a winding47w. Energization of the solenoid 47 causes the clutch to engage therotating fly wheel 4l'which in turn reciprocates the ram 38 through onecycle.

Normal and proper operation of the control system will now be described.With the ram 38 at the top of its stroke, the limit switch 11 is closed,and the bolster plate 44 is in its outer or load position because thebolster-out solenoid 46 is energized through the circuit from theconductor Ll, the contactslla, a conductor Ll, the contacts 31d, ajunction 50, the contacts 33c and the winding 46w to the conductor L2.

Depression of the push buttons 21 and 22 causes energization of thewinding 31w from the conductor L1 through the contacts 21a, 22a, and12d, a junction 52 and the winding 31w to the conductor L2, and causesenergization of the winding 32w from the conductor L1 through thecontacts'2la, 22a, 120, a junction 54, the diode 35 and the winding 32wto the conductor L2. Opening of the contacts 310' upon energization ofthe winding 31w effects deenergization of the bolster-out solenoid 46,and closure of the contacts 310 effects energization of the bolster-insolenoid 45 by a circuit from the junction 54 through the contacts 13b,14b, and 31a and the winding 45w to the conductor L2 thus causing thebolster plate 44 to move inwardly toward the work position. The contacts31b and 310 also close, as do the contacts 32a, but they perform nofunction at this time. Opening of the contacts 32b also is withoutresult.

When the bolster plate 44 is a short distance from its full-in or workposition, the bolster plate contacts an arm of the limit switch 12. Theinitial movement of the arm results in the closing of contact 12a andthe opening of contact 120. The closing of contact 120 completes aholding circuit for the winding 31w through the now closed contacts 31cand 12a and the junction 52. As the arm of the switch 12 is movedfurther by the bolster plate, contact 12d opens and contact 12b closes.The opening of contact 12d interrupts the circuit to the winding 31wthrough the contacts 21a and 22b and thereby eliminates any possibilityof current flow from the junction 52 to the junction 54. The contact 12bcloses so that the junction 54 remains connected to the conductor L1through the contacts 21a and 22a.

Upon the bolster plate 44 reaching the work position, the limit switches13 and 14 trip. Tripping of the limit switches 13 and 14 opens thecontacts 13b and 14b and closes the contacts 13a and 14a. Opening of thecontacts 13b and 14b interrupts the energizing circuit for thebolster-in solenoid 45, but the closure of the contacts 13a and 14bcompletes no circuit so long as the push buttons 21 and 22 remaindepressed.

Normally, both of the push buttons 21 and 22 are released simultaneouslyshortly after the bolster plate 44 reaches the position where limitswitch 12 is actuated. Assuming such a simultaneous release, thecontacts 21a and 22b both open together and the contacts 21b and 22bboth close together. Opening of the contacts 21a and 22b causesdeenergization of the winding 32w after a brief time delay effected bythe diode 35 and the capacitor 36. Before the relay 32 drops out therebyopening its contact 32a and closing its contact 32b, the winding 33w isenergized from the conductor L1 through the now-closed contacts 21b,22b, 32a, and 31b and the winding 33w to the conductor L2. The relay 33picks up and is held in that position against the opening of thecontacts 32a by closure of its contacts 33b which are connected directlyin parallel with the contacts 32a. The opening of the contacts 33cinterrupts a circuit to the bolster-out solenoid winding 46w to insurethat the bolster plate 44 does not move out of the work position at thistime. Upon pick-up of the relay 33, the contacts 33a also close tocomplete an energizing circuit for the clutch solenoid winding 47w fromthe conductor L1 through the contacts 21b, 22b, 33b, 31b, 13a, 14a, and33a and the winding 47w to the conductor L2. Energization of the clutchsolenoid 47 causes the press ram 38 to start a cycle.

As soon as the ram 38 starts its cycle, the contacts 11a open to effectde-energization of the relays 31 and 33. When the ram 38 again reachesthe top of its stroke, the contacts 11a close and complete the circuitthrough the now-closed contacts 31d and 33c to the winding 46w of thebolster-out solenoid 46 causing the bolster plate 44 to move outward tothe load position for unloading and reloading preparatory to anothercycle.

It sometimes happens that an operator releases one or both of the pushbuttons 21 and 22 too soon and before operation of the limit switch 12.In this case, the winding 31w is immediately de-energized and alwaysbefore the ram 38 starts its cycle. Consequent drop-out of the relay 31causes closing of the contacts 31d to energize the bolster-out solenoid46 and the bolster plate 44 returns to the load position. The cycle thenhas to be initiated again by closure of both run buttons 21 and 22.

If the push buttons 21 and 22 are released nonsimultaneously afteroperation of the limit switches 12, 13 and 14, release of the first onecauses the relay 32 to start timing out. if the relay 32 drops outbefore the other run button is released, the release of the other buttoncauses the winding 46w of the bolster-out solenoid 46 to be energizedthrough the contacts 21b, 22b, 32b and 330 and the bolster plate 44moves out to the load position.

Thus it is apparent that there has been provided, in accordance with theinvention, a control system for a punch press that fully satisfies theobjects, aim, and advantages set forth above. While the invention hasbeen described in conjunction with specific embodiments thereof, it isevident that many alternatives, modifications, and variations will beapparent to those skilled in the art in light of the foregoingdescription. Accordingly, it is intended to embrace all suchalternatives, modifications, and variations as fall within the spiritand broad scope of the appended claims.

I claim:

1. A punch press control system wherein a pair of push buttons must bothbe depressed to complete a first electric circuit which, when completed,causes operation of means for moving a bolster plate of the punch pressfrom a loading to a work position, limit switch means responsive to thebolster plate reaching the work position partially completes a secondelectric circuit which, when completed, causes operation of a means foreffecting reciprocation of a ram of the punch press through one cycle,and release of both push buttons completes the second circuit, saidsystem being characterized in that time delay means are provided toprevent completion of the second circuit if the release of one of thepush buttons is delayed beyond a predetermined time after release of theother push button.

2. A punch press control system as claimed in claim 1 wherein the systemincludes a relay having a coil in a circuit energized concurrently withthe first circuit and a normally open contact in the second circuit,said contact closing upon energization of the coil, said coil beingassociated with the time delay means thereby to delay deenergization ofthe relay coil upon opening of the first circuit.

3. A punch press central system as claimed in claim 2 wherein the timedelay means includes a diode and a capacitor connected in series andparallel, respectively, with the coil.

4. In a control system for a punch press of the type having a bolsterplate reciprocatable between a loading position and work position and aram reciprocatable through a cycle from a first to a second relativelydisplaced position and back to the first position, said control systemcomprising: first, second and third electromagnetic relays each havingan energizing circuit; a bolster-in solenoid having an energizingcircuit and operative when energized to cause the bolster plate to movefrom the loading position to the work position; a bolster-out solenoidhaving an energizing circuit and operative when energized to cause thebolster plate to move from the work position to the loading position; aram solenoid having an energizing circuit and operative when energizedto cause the ram to reciprocate through said cycle; a pair ofdepressible and releasable push buttons each having a normally open anda normally closed contact, the normally open contacts of the pushbuttons being connected in series with each other in a circuit formingpart of the energizing circuits for the first and second relays and thebolster-in solenoid, the energizing circuits for the first and secondrelays being completed upon closure of the normally open contacts ofboth push buttons when the bolster plate is in the loading position; anormally open contact of the first relay in the energizing circuit forthe bolster-in solenoid which contact when closed completes theenergizing circuit for the bolster-in solenoid through the normally opencontact of the push buttons when those contacts are closed and thebolster plate is not in the work position; the normally closed contactsof the push buttons being connected in series with each other in acircuit forming part of the energizing circuits for the third relay andthe ram and bolster-out solenoids; a normally open contact of each ofthe first and second relays being connected in series with each other ina circuit forming part of the energizing circuits of the ram solenoidand the third relay; a normally open contact of the third relay beinginterposed in the energizing circuit for the ram solenoid; theenergizing circuit for the third relay being completed when the normallyclosed contacts of the push buttons are closed and the first and secondrelays are energized and the energizing circuit for the ram solenoidbeing completed upon energization of the third relay; normally closed ofthe second and third relays being in series with each other in theenergizing circuit for the bolster-out solenoid and in series with thenormally closed contacts of the push buttons, the improvement whichcomprise means to provide a time interval in the drop-out of the secondrelay so that both push buttons must be released simultaneously orwithin a predetermined time of each other to open their normally opencontacts and to close their normally closed contacts thereby to causeenergization on the ram-solenoid.

1. A punch press control system wherein a pair of push buttons must bothbe depressed to complete a first electric circuit which, when completed,causes operation of means for moving a bolster plate of the punch pressfrom a loading to a work position, limit switch means responsive to thebolster plate reaching the work position partially completes a secondelectric circuit which, when completed, causes operation of a means foreffecting reciprocation of a ram of the punch press through one cycle,and release of both push buttons completes the second circuit, saidsystem being characterized in that time delay means are provided toprevent completion of the second circuit if the release of one of thepush buttons is delayed beyond a predetermined time after release of theother push button.
 2. A punch press control system as claimed in claim 1wherein the system includes a relay having a coil in a circuit energizedconcurrently with the first circuit and a normally open contact in thesecond circuit, said contact closing upon energization of the coil, saidcoil being associated with the time delay means thereby to delaydeenergization of the relay coil upon opening of the first circuit.
 3. Apunch press central system as claimed in claim 2 wherein the time delaymeans includes a diode and a capacitor connected in series and parallel,respectively, with the coil.
 4. In a control system for a punch press ofthe type having a bolster plate reciprocatable between a loadingposition and work position and a ram reciprocatable through a cycle froma first to a second relatively displaced position and back to the firstposition, said control system comprising: first, second and thirdelectromagnetic relays each having an energizing circuit; a bolster-insolenoid having an energizing circuit and operative when energized tocause the bolster plate to move from the loading position to the workposition; a bolster-out solenoid having an energizing circuit andoperative when energized to cause the bolster plate to move from thework position to the loading position; a ram solenoid having anenergizing circuit and operative when energized to cause the ram toreciprocate through said cycle; a pair of depressible and releasablepush buttons each having a normally open and a normally closed contact,the normally open contacts of the push buttons being connected in serieswith each other in a circuit forming part of the energizing circuits forthe first and second relays and the bolster-in solenoid, the energizingcircuits for the first and second relays being completed upon closure ofthe normally open contacts of both push buttons when the bolster plateis in the loading position; a normally open contact of the first relayin the energizing circuit for the bolster-in solenoid which contact whenclosed completes the energizing circuit for the bolster-in solenoidthrough the normally open contact of the push buttons when thosecontacts are closed and the bolster plate is not in the work position;the normally closed contacts of the push buttons being connected inseries with each other in a circuit forming part of the energizingcircuits for the third relay and the ram and bolster-out solenoids; anormally open contact of each of the first and second relays beingconnected in series with each other in a circuit forming part of theenergizing circuits of the ram solenoid and the third relay; a normallyopen contact of the third relay being interposed in the energizingcircuit for the ram solenoid; the energizing circuit for the third relaybeing completed when the normally closed contacts of the push buttonsare closed and The first and second relays are energized and theenergizing circuit for the ram solenoid being completed uponenergization of the third relay; normally closed of the second and thirdrelays being in series with each other in the energizing circuit for thebolster-out solenoid and in series with the normally closed contacts ofthe push buttons, the improvement which comprise means to provide a timeinterval in the drop-out of the second relay so that both push buttonsmust be released simultaneously or within a predetermined time of eachother to open their normally open contacts and to close their normallyclosed contacts thereby to cause energization on the ram-solenoid.